The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
During a combustion cycle of an internal combustion engine (ICE), air/fuel mixtures are provided in cylinders of the ICE. The air/fuel mixtures are compressed and combusted to provide output torque. After combustion, pistons of the ICE force exhaust gases in the cylinders out through exhaust valve openings and into an exhaust system. The exhaust gases may contain nitrogen oxides (NOx), carbon monoxide (CO) and hydrocarbons (HCs).
An exhaust gas treatment system of the ICE may include a catalytic converter and a selective catalytic reduction (SCR) catalyst to reduce exhaust emissions. As an example, a thee-way catalyst converter (TWC) may be used to reduce NOx, CO2 and HCs within an exhaust system. The TWC converts NOx to nitrogen and oxygen, CO to carbon dioxide and oxidizes unburnt HCs to produce carbon dioxide and water. The SCR catalyst may be located downstream from the TWC and may further reduce NOx in the exhaust system. A SCR catalyst converts NOx into nitrogen N2 and water H2O.